426 M. A. Naquet on the Calculus 



notation without the speculations explanatory of the^me iso- 

 mers mentioned above. Are these speculations, which could 

 be perfectly well rejected even with our existing notation, 

 out of date and already useless ? I do not think so. They 

 may become useless one day. We shall perhaps find in ther- 

 mochemistry the means of explaining these fine isomers, and 

 applying to them mathematical expressions. But until then 

 these speculations appear to us useful, because they arrange 

 facts which would otherwise remain without arrangement; 

 and they correspond well enough to the actual phenomena to 

 allow us to determine, notably in the aromatic series, the 

 number of these fine isomers possible for each term of the 

 series. 



Even if we do not take into consideration the extreme dif- 

 ficulty that there is in replacing one notation by another, and 

 the momentary confusion introduced by it into science, a con- 

 fusion which ought not to be permitted unless the change 

 offers an undeniable advantage, even if we do not take into 

 consideration this difficulty, we should oppose the immediate 

 adoption of Sir B. C. Brodie's notation, because it seems to 

 us to open the door to a crowd of suppositions more consider- 

 able than those it aims at eliminating, and because, from the 

 point of view of the arrangement and anticipation of facts, it 

 does not provide us with the means of dispensing with those 

 atomic speculations which, without being intimately connected 

 with the existing notation, may nevertheless be joined to it, 

 and cannot in any case be adapted to the notation of Sir B. 

 C. Brodie. 



Are we then to conclude that Sir B. C. Brodie's work has 

 no value ? Far from us indeed be such a thought. If we had 

 been of this opinion, we should not have taken the trouble to 

 translate it. It opens out a new method which, enlarged and 

 perfected, will permit the application of Algebra to Chemistry, 

 and the substitution for our " system of chemistry " of a true 

 " theory of chemical events." Even if this result be not pro- 

 duced, if the imperfections with which we charge the new me- 

 thod of notation continue to exist, if there only remain of the 

 notation of Sir B. C. Brodie his hypothesis a, including that 

 of the compound constitution of chlorine, nitrogen, potas- 

 sium, and their compounds, the work would still be useful. 



As long as we have to do with a " system," a hypothesis 

 with no other object than that of arranging known facts and 

 discovering new facts, two different hypotheses may legiti- 

 mately be employed, provided that they answer to the requi- 

 site conditions. It is thus that the hypotheses of emission 

 and undulations have long been tacitly accepted in Optics. It 



